Patterns of damage in the mature neonatal brain.

Patterns of damage in the mature neonatal brain can be subdivided into focal, multifocal and diffuse. The main cause of diffuse brain damage in the term newborn is hypoxic-ischaemic encephalopathy (HIE). HIE is still the major recognized perinatal cause of neurological morbidity in full-term newborns. MRI offers today the highest sensitivity in detecting acute anoxic injury of the neonatal brain. Conventional acquisition techniques together with modern diffusion techniques can identify typical patterns of HIE injury, even in the early course of the disease. However, even though highly suggestive, these patterns cannot be considered as pathognomonic. Perinatal metabolic disease such as kernicterus and severe hypoglycaemia should be differentiated from classic HIE. Other conditions, such as infections, non-accidental injury and rarer metabolic diseases can be misinterpreted as HIE in their early course when diffuse brain swelling is still the predominant MRI feature. Diffusion techniques can help to differentiate different types of diffuse brain oedema. Typical examples of focal injuries are arterial or venous infarctions. In arterial infarction, diffusion techniques can define more precisely than conventional imaging the extent of focal infarction, even in the hyperacute phase. Moreover, diffusion techniques provide quantitative data of acute corticospinal tract injury, especially at the level of the cerebral peduncles. Venous infarction should be suspected in every case of unexplained cerebral haematoma in the full-term newborn. In the presence of spontaneous bleeding, venous structures should always be evaluated by MR angiography.